Field of the Disclosure
The present disclosure relates to an ESD protection device. “ESD” stands for electro-static discharge. ESD is a phenomenon in which a strong discharge is generated when a charged conductive object, for example, a human body, comes into contact with or comes sufficiently close to another conductive object. An “ESD protection device” is a device for allowing an electric charge to flow to GND and protecting a circuit, when an electrostatic discharge is generated.
Description of the Related Art
These days, ESD protection devices for protecting electronic apparatuses from an electrostatic discharge are widely used.
An example of a circuit where an ESD protection device is used is illustrated in FIG. 13. A circuit to be protected (hereinafter called a “protected circuit”) 502 is electrically connected to a terminal 503. The protected circuit 502 is, for example, an integrated circuit (IC). The terminal 503 represents a portion where a conductor or the like is exposed to the outside in a connector or the like. An ESD protection device 501 is connected to an end of a wiring line branching from a midpoint of a wiring line connecting the protected circuit 502 and the terminal 503 to each other. The ESD protection device 501 and the protected circuit 502 are separately grounded. As illustrated in FIG. 13, in a normal state, the discharge electrodes within the ESD protection device 501 are in a state in which a current does not flow between the discharge electrodes. When an ESD is generated as a result of, for example, a human body coming into contact with or coming sufficiently close to the terminal 503, a high voltage is applied to the terminal 503. At this time, without taking any steps, an overvoltage is applied to the protected circuit 502 and a current will flow as indicated by an arrow 92. However, when a discharge is generated between the discharge electrodes of the ESD protection device 501, a current will flow in a direction indicated by an arrow 91 due to the discharge and, hence, an overvoltage is not applied to the protected circuit 502. In other words, the protected circuit 502 is protected.
For example, Japanese Unexamined Patent Application Publication No. 2009-238563 (Patent Document 1) discloses a structure called an “overvoltage protection component” in which a hollow functioning as a discharge portion is formed inside a base body formed of an insulator and discharge electrodes face each other within this hollow. It is disclosed in Patent Document 1 that the discharge electrodes are formed by printing, plating, or the like.
For example, Japanese Unexamined Patent Application Publication No. 2001-217057 (Patent Document 2) discloses a structure called a “chip-type surge absorption device” in which internal electrodes face each other inside an insulating ceramic sintered body. A discharge space is formed so as to be interposed between the internal electrodes. It is disclosed in Patent Document 2 that the discharge space is filled with a carbon paste by using screen printing, and the carbon paste is burnt down at sintering time.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2009-238563    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2001-217057